1. Nutrient Requirements of Horses Presentation Part 2: Energy (Continued) #8895-C

2. Requirements Many factors affect energy needs: – Individuality of horse – Body makeup – Temperature & humidity of environment

3. Requirements How much energy is expended influenced by: – How intensely & how long a horse works – Rider ’ s ability & weight – Condition of the surface where horse works

4. Requirements - Maintenance Energy needed for maintenance Maintenance energy = energy needed to sustain body weight while performing non- work activities Weight used to calculate maintenance energy requirement

5. Requirements - Maintenance Maintenance DE (Mcal/day) = 1.4 + 0.03 (W) is horse ’ s weight (600 kg or less)

6. Requirements - Maintenance Different formula for horses weighing more than 600 kg Larger horses move around less voluntarily Previous formula overestimates energy needs of bigger horses

7. Requirements - Maintenance Maintenance DE (Mcal/day) = 1.82 + 0.0383(W) – 0.000015 (W x W)

8. Requirements - Maintenance Visit National Research Council ’ s publication, “ Nutritional Requirements of the Horse ” to devise a ration Tailor feedings to meet the needs of “ easy keepers ” or “ hard keepers ”

9. Requirements - Maintenance Easy keepers do not need as much feed as hard keepers do to stay fat Notice if horses get fat or thin – Adjust feed accordingly

10. Requirements - Maintenance If horses eat too much, they will become obese – Especially if not getting enough exercise If they do not get sufficient energy, horses will: – Lose weight – Lose condition – Become tired easily

11. Requirements - Reproduction Important mares have good body condition at breeding time Body condition influences rate of conception – Conception - act of becoming pregnant

12. Requirements - Reproduction If horse is thin but gaining weight at breeding time, they are twice as likely to conceive, than if thin & maintaining In thin horses, estrus cycle may be delayed & irregular May fail to ovulate, conceive, or maintain pregnancy

13. Requirements - Reproduction Estrus - heat cycle of reproduction Ovulate - to release the egg during the estrus cycle Good or fat condition = high conception rates

14. Requirements - Reproduction Body condition score determines need for energy in diet Thin mares - energy intake increases 10-15% above nutritional requirement – Helps to put on weight – Exhibit higher condition score

15. Requirements - Reproduction Too fat - energy intake decreases 10-15% below the nutritional requirement – Helps to lose weight – Have lower condition score

16. Requirements-Gestation Last three months - fetus develops most & energy requirement increases greatly To get estimate of amount of DE needed, multiply maintenance needs by: – 1.11 - ninth month – 1.13 - tenth month – 1.20 - eleventh month

17. Requirements-Gestation For example: – 500 kg mare – Tenth month of gestation 16.4 Mcal x 1.13 = 18.5 Mcal/day of DE

18. Requirements - Lactation Lactating mares produce large amounts of milk in early lactation (weeks 1-12) – 3% of body weight For example: A 500 kg mare generates 15 kg – 33.6 lbs of milk daily

19. Requirements - Lactation Percentage reduces to 2% of body weight/day in late lactation (13-24 weeks) DE depends on content & amount of milk 792 Kcal of DE are needed to produce 1 kg of milk

20. Requirements - Growth To calculate energy needs for maintenance & growth use the following formula: Maintenance & Growth DE (Mcal/day) = [Maintenance DE] + [4.81 + 1.17(X) – 0.023(X x X)][ADG] – ADG - average daily gain – X - horse ’ s age in months

21. Requirements - Growth If fed too much energy, some may grow way too fast for the increase of their body weight Can influence soundness & life expectancy May develop developmental orthopedic disease (DOD)

22. Requirements - Growth DOD - various types of bone disorders such as: – Enlargements & deformities of ankles knees, & hocks – Contraction of pastern tendons If ration altered too quickly by adding energy, horse may develop DOD

23. Requirements - Work Determining DE requirements for work is difficult Many factors cannot be measured Some of these include: – Condition & training of animals – Ability & weight of rider – Composition of diet

24. Requirements - Work Energy requirements divided into light, medium, & intense work Light Work: – Hunter flat work – Western pleasure

25. Requirements - Work Medium work: – Ranch work – Roping – Cutting – Barrel racing – Jumping Intense Work: – Racing – Polo

26. Requirements - Work Energy needs may vary due to: – Type of horse – Type of work – Size of load